A representative gas detected by an electrochemical gas sensor includes CO2. CO2 gas is harmless and is an element inevitable for photosynthesis of plants, but an amount of CO2 has increased continually along with the development of the civilization, causing environmental problems such as global warming or abnormal climate due to the green house effect. Accordingly, CO2 gas sensors for regulating carbon credits in the industrial field or exhaust gases of vehicles are being increasingly demanded.
Meanwhile, currently, optical gas sensors using non-dispersive infrared absorption (NDIR) are being mainly used as CO2 gas sensors. While the optical gas sensors can realize an accurate measurement, have a long life span, and show stability, they cannot be easily used as a general sensor due to their high prices and may cause errors in a humid environment.
Studies on potentiometric electrochemical gas sensors are being actively made using solid ionic conductors (solid electrolyte) as sensors capable of overcoming the disadvantage of the optical gas sensors. An electrochemical gas sensor has a simple structure, shows an excellent gas selectivity, and allows a detection of a gas having low concentration of a ppm level. In addition, since electrochemical gas sensors can be manufactured at a low price as compared with the optical gas sensors, there is a high possibility of using the electrochemical gas sensors as a distributed gas analyzer or a general sensor available for homes or offices.
Meanwhile, methods of manufacturing gas electrochemical gas sensors according to the related art include a method of depositing a detection electrode and a reference electrode on one surface of a solid electrolyte ceramic and depositing a high temperature heater for an operation of the sensor on an opposite surface thereof, and a method of stacking a solid electrolyte thick film, a detection electrode, and a reference electrode on one surface of a substrate formed of alumina or quartz and depositing a sensor operating heater on an opposite surface thereof to manufacture an electrochemical gas sensor.
Since the bulk electrochemical gas sensors are resistant to a sudden impact, but require high power consumption and a big size to maintain a high temperature for an operation of the sensor, It is difficult to apply the bulk electrochemical gas sensors to portable terminals or ubiquitous sensor network (USN) sensor nodes.
Accordingly, in order to allow an electrochemical gas sensor to be mounted to a portable terminal, a USN sensor network or the like as a general sensor, a MEMS electrochemical gas sensor needs to consume little power, have a small size, and be mass-produced.
The present disclosure has been made in an effort to provide a MEMS electrochemical gas sensor which has an ultra small size and significantly reduces power consumption.
The present disclosure also has been made in an effort to provide an MEMS electrochemical gas sensor which provides services in various environments.
An exemplary embodiment of the present disclosure provides a MEMS electrochemical gas sensor, including: a substrate a lower central region of which is etched by a predetermined thickness; a first insulation film formed on the substrate; a heat emitting resistance body formed on the first insulation film; a second insulation film formed on the heat emitting resistance body; a reference electrode formed in an upper central region of the second insulation film; a solid electrolyte formed on the reference electrode; and a detection electrode formed on the solid electrolyte.
Another exemplary embodiment of the present disclosure provides a MEMS electrochemical gas sensor, including: a substrate a lower central region of which is etched by a predetermined thickness; a first insulation film formed on the substrate; a heat emitting resistance body formed on the first insulation film; a second insulation film formed on the heat emitting resistance body; a solid electrolyte formed in an upper central region of the second insulation film; a reference electrode formed at one side of an upper portion of the solid electrolyte; and a detection electrode formed at an opposite side of the upper portion of the solid electrolyte.
According to the exemplary embodiments of the present disclosure, power consumption is reduced, as compared with an existing bulk electrochemical gas sensor, by providing an MEMS electrochemical gas sensor where a substrate is etched by a predetermined thickness to thermally isolate insulation films and a heat emitting resistance body.
Further, signal processing/transmitting circuits can be integrated on a substrate by using a semiconductor process and accordingly can be mounted to various systems (for example, a portable terminal, a sensor node or the like) while realizing various services in an extreme environment, by providing a MEMS electrochemical gas sensor having a vertical detection electrode/solid electrolyte/reference electrode structure.
In addition, a MEMS electrochemical gas sensor having low-power characteristics can be used for a long period of time even within a restricted battery capacity, and can be stably driven by using a self-charged power source in various environments where energy converting elements such as a thermoelectric element, a piezoelectric element and the like are operated.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.